Saturday, July 9, 2011

Home Made Precision Stylus Force Gauge

I love my Thorens TD-145 turntable, but it has one glaring idiosyncrasy. The stylus force is set with a dial gauge on the mount that is connected to a spring on the rear of the tonearm via a thin cable. As you turn the dial to change the force, you tighten/loosen the spring attached to the cable.

What this means is that when you raise the tonearm, you pull harder on the cable, stretching the spring, and the force increases. If you lower the arm, the force decreases.

So, checking he force with a scale can only be done with the scale pan at the same height as the record surface.

Originally I just took the platter off and set the scale on something to raise the pan 1.25" from the plinth (turntable base)

Looking at scales online, I saw a $100 scale that was made with a pan with an extension that is a better version of what I made.

I copied the design by using a cut up credit card with wood toothpicks gorilla glued on for stiffness.

When you take the record off the platter, and put the scale on the mat, the weigh point is very close to the same height as the upper surface of a record. Now, measuring the force becomes very easy.

This all started because my tracking force was significantly off when using the dial force gauge. I suppose the spring has weakened over the last 40 years. You can use a screwdriver to change the spring tension. There is a small tube on the back of the tonearm that is threaded on the inside. You can see the counterweight cutout for the tube. When you screw in the plug from the rear, you reduce tension on the spring, and reduce stylus force.

I knew that I wanted 1.75 grams, so I balanced the tonearm to zero by moving the counter weight, with the dial set to zero. Then I set the stylus force to 1.75 grams, and adjusted the spring until the scale read 1.75g. The scale reads to within a couple hundredths of a gram where ever the scale is set. Now I can trust the dial gauge when I change cartridges.

I have several good Phono Cartridges. I have seen them all at $350 (each) on eBay. The designs out of the 70's seems to command a premium. It was the height of demand for vinyl. The 80's saw the introduction of CD's.

I read about shops that stopped setting turntables 30 years ago that are starting to sell lot of them again. Audiophiles are rediscovering the sound of vinyl.

I just bought Allison Krause and Union Stations "Paper Airplane" album. It came with a free digital download card. I then downloaded the album as a wave files (the same as a CD). I look at it as a digital download with free vinyl album.

Goldring G900SE by far my favorite
Shure V15 type 3 (Type 3G body with .3x.7mil elliptical stylus. The "G" indicated a conical stylus.
Goldring G900E grey body, designed for high mass tonearms to track at up to 3 grams. This cartridge with a black SE stylus
Audio Technica AT13Ea
Audio Technica AT15XE and a separate ATN15 stylus with a Shibata stylus from an AT15Sa cart.
Micro Acoustics 2002E (good electret type)
Ortofon M20E Super
Ortofon VMS 20E Mk II

The cartridge is a Satin M-117G high output moving coil cartridge. Worth about $350 ish today. Tracking force is recommended 1-2 grams, but I find heavier tracking force reduces mist-tracking which makes the sound suck, and damages the record.

I really hope one of my kids grabs the hi-fi and record collection. You might not like Miles Davis "Kind of Blue" at 19, but you probably will at 25, and for shure by 29.

There is a wealth of wonderful music available at used record shops. Things you will never find on CD or digital. Listening to a record is a very relaxing thing to do. It becomes an activity like watching a movie, and makes the music much better.


Darcy Hubbert said...

These are definitely big boy's toys! Pretty impressive. Thanks for sharing!

Amber Barnes said...

This article is absolutely great! There's so much to learn from this. Precission really counts so much. Thanks for sharing!

Leslie Porter said...

These gadgets are great. I'm pretty much impressed with these. These are indeed awesome when it comes to precision. Force gauge is very important in measuring push or pull test across all industries. This is applicable in research and development, laboratory, quality, production and field environment. Thanks for sharing this article.